Speakers
Ana Amelia Machado
Ettore Segreto
Description
The idea of the ARAPUCA was proposed in 2015 with the goal of satisfying the need for a device with a good detection efficiency (at the level of few percent) over a large area (tenths of a squre meter or more), for large scale liquid argon experiments. The great novelty introduced by this device is represented by its capability of trapping photons inside a cavity with highly reflective internal surfaces, observed by an array of active silicon sensors (SiPMs). The core of the device is represented by its acceptance window, made by a combination of a shortpass dichroic filter and two different wavelength shifters, which allows the photons to enter the reflective cavity, but not to exit from it. Trapped photons can bunch multiple times on the highly reflective internal surfaces up to being or detected or absorbed, with the net effect of increasing the overall detection efficiency with respect to the case of a bare SiPM array. Two arrays of 16 ARAPUCAs have been installed inside the protoDUNE at the end of 2017 and are still taking data. Preliminary data analysis shows very good performances, in line with the expectatiations. The ARAPUCA design has been recently improved with the introduction of a light guide inside the reflective cavity, which will allow to improve the photon detection efficiency of about 40% (X-ARAPUCA). The X-ARAPUCA currently represents the baseline design for the Photon Detection System of the single phase DUNE far detector.
